The number of six-digit numbers, all digits of which are odd is ______.

In a football championship, 153 matches were played . Every two teams played one match with each other. The number of teams, participating in the championship
is ______.

The total number of ways in which six ‘+’ and four ‘–’ signs can be arranged in a line such that no two signs ‘–’ occur together is ______.

A committee of 6 is to be chosen from 10 men and 7 women so as to contain atleast 3 men and 2 women. In how many different ways can this be done if two particular women refuse to serve on the same committee.

A box contains 2 white balls, 3 black balls and 4 red balls. The number of ways  threeballs be drawn from the box if at least one black ball is to be included in the draw is ______.

Three letters can be posted in five letterboxes in 3^5 ways.

In a steamer there are stalls for 12 animals, and there are horses, cows and calves (not less than 12 each) ready to be shipped. They can be loaded in 3^12  ways.

If some or all of n objects are taken at a time, the number of combinations
is 2^n–1.

There will be only 24 selections containing at least one red ball out of a bag containing 4 red and 5 black balls. It is being given that the balls of the same colour are identical.

A candidate is required to answer 7 questions out of 12 questions which are divided into two groups, each containing 6 questions. He is not permitted to attempt more than 5 questions from either group. He can choose the seven questions in 650 ways.

Which of the following gas has highest contribution in global warming?

1) Carbon-di-oxide

2) Chlorofluorocarbon

3) Nitro us oxide

4) Methane